But, with 20 people inside the venue, the attempted attack would have had ''catastrophic consequences'', with a number of lives lost or hurt and serious damage to property, police said.

The head of the NSW Police gangs squad, Detective Superintendent Arthur Katsogiannis, said Samy Duong, 40, a Comanchero member, of no fixed abode, was charged on Tuesday with attempt to damage property with an explosive device after being arrested at the Mercure Hotel in Liverpool.

''There was a real danger someone could have been hurt or died,'' Superintendent Katsogiannis said. ''From our perspective this has taken it to another level.''

A police source said Mr Duong, who changed his name by deed poll, was a new Comanchero member.

A Mill Hotel manager, who wished to remain anonymous, said despite the potentially deadly consequences their Nepalese cleaner was relaxed about his find. ''He said 'in my country this looks like a bomb' and we then called police,'' the manager said.

The Comanchero have one of their strongest chapter club houses in Milperra and in the 1980s the Viking Tavern was a famous bikie haunt. Nowadays, the hotel is better known for its swish surrounds, beer garden and menu.

In early July the hotel's manager said security had barred entry to Comanchero members.

''We've never had any trouble with that group before but we have a strict policy against any bikie colours in the bar,'' he said.

Superintendent Katsogiannis would not confirm this was the motive, but he ruled out a bikie war or internal Comanchero fighting, as seen earlier this month.

''We have two solid lines of inquiry that at this stage I don't want to confirm as the motive,'' he said.

In 2009 the now defunct Notorious bikie gang was allegedly behind the bombing of the Hell's Angels Petersham club house.